Where is it mentioned that Agassi benches 300lbs? Thats practically doing 6 45 lbs plates. The most I ever benched was 295 lbs, my one rep max, back when I played football. That is 4x45 lbs plates and 2x35 lbs plates.
In football, we trained like power lifters, and did lots of squats, and clean and press type exercises with high explosion movements.
If Andre does bench that much then he is training to be bulk up as what vin mentioned.
Its really impressive Andre can bench that much considering his upper body does not have the mass that most people have that can bench about 300 lbs.